Core memory delta noise cancellation

ABSTRACT

Method and means for delta noise cancellation for memory systems in which the delta noise decay function is combined electronically with a separately generated function derived from the delta noise decay function to cancel or reduce the delta noise amplitude in the decaying period to improve memory access time.

United States Patent [151 3,643,171

Chang 1451 Feb. 15, 1972 [54] CORE MEMORY DELTA NOISE 3,387,221 6/1968Arberman et al ..328/163 CANCELLATION 3,094,665 6/1963 Wildman ..328/165[72] Inventor: Hua-Shan Chang, South Pasadena, Calif. ()TH ERPUBLICATIONS [73] Asslgnee: ggg Alrcra Corporation Burbank Adaptive FSKData Demodulator" by R. W. Calfee. lBM Technical DisclosureBulletin,Vol. 5,No. LApr. 1963.p. 76 [22] Filed: Nov. 6, 1970 (Copy in328/1 16) 21 A LN 87 41 1 pp 0 ,5 Primary ExaminerDonald D. ForrerAssistant Examiner-Harold A. Dixon [52] US. Cl. ..328/l65, 328/1 17,307/231 mmmey (;eorge C Sullivan [51] Int. Cl. ..H04b 1/12 [58] FieldofSearch ..330/69; 307/231; 328/116, 1 17, TR!

328/165, 163 [57] ABS CT Method and means for delta noise cancellationfor memory [56] References Cited systems in which the delta noise decayfunction is combined electronically with a separately generated functionderived 1 UNTED STATES PATENTS from the delta noise decay function tocancel or reduce the 2,450,818 10/1948 Vermillion ..325/467 delta noiseamplitude in the decaying period to improve 3,328,704 6/1967 Wantland..328/1l7 memory access time- 2,534,264 12/1950 Hoeppner ..328/1173,119,070 1/1964 Seliger .323/114 1 cla'ms4maw'ng V in (t) Vowreneurmros mumeuen SUM V out GAIN V in ('r) SHEET 1 OF 2 0|FFERENTIATOR GAIN FIG.

Romp inpui MULTIPLIER sum Voui l I RE i Ccmstont I \,Q5

INVENTOR.

HUA-SHAN CHANG Agent Vou? PMENTEDFEB 15 ran SHEET 2 OF 2 V out (i) SUMDIFFERENTIATOR GAIN Vin (t) FIG. 3

V out l Conston? I RE2 INVENTOR. HUA-SHAN CHANG Agent CORE MEMORY DELTANOISE CANCELLATION This invention relates to noise cancellation and moreparticularly to delta noise cancellation to improve the core memoryaccess time.

The inherent limitation on the access time of a large core memoryusually lies in the slow decay of the delta noise in the sense lines.Normally, the delta noise decays according to an exponential function ifthe line is properly terminated. Previous attempts to differentiate thedecay function with the hope that it will reduce to zero faster and bemore predictable have been unsuccessful.

It is therefore an object of the present invention to provide animproved method for cancellation or reducing the delta noise amplitude.

Another object of the invention is to improve the memory access time.

These and other objects of the invention will become more apparent fromthe following description when taken with the accompanying drawings inwhich:

FIG. I is a block diagram of one embodiment of the invention;

FIG. 2 is a schematic showing a typical implementation of FIG. I;

FIG. 3 is a block diagram of a second embodiment of the invention;

FIG. 4 is a schematic showing a typical implementation of FIG. 3.

The sense line in a memory system may be compared to a transmission linewith the cores evenly spaced on the line. Analysis shows that after thecurrent has reached the threshold of the minor wall displacement (on thehysteresis loop), the delta noise waveform follows the equation a-bexp(t) up to !=T, where Tis the total delay of the sense line. If theline is properly terminated, the delta noise will then decayexponentially. Otherwise, the decay of the delta noise can beapproximated by the function /(t+l where n can be determined from thelength of the sense line and the reflection coefficient of thetermination. The present invention utilizes the characteristics of theapproximated decay function to cancel or substantially reduce the deltanoise.

DIFFERENTIATION MULTIPLICATION Referring to FIG. I, a block diagram ofthis method is shown. This embodiment utilizes the distinctivecharacteristic of the delta noise decay function /(t+1)". Observe thatthe product of its derivative and a ramp function is the originalfunction. Thus, the block diagram represents the following equation:

Vout (t) Vin (t) 1) Substituting in equation (1), we have:

can

from which it is readily observed that the output is zero. The coreturnover signal, which is represented by Sinw I, will be partiallydifferentiated in the output.

FIG. 2 represents a typical schematic to implement the block diagram ofFIG. 1. The input signal is differentiated by the RC network and thenmultip red with the ramp function by means of the transistor circuitsQrQz. Q converts the ramp voltage to ramp current. The result is thenadded by QrQ Their emitter resistors RE determine the gain of thecircuit. The resistors RE are connected to a constant current source.For the delta noise to be cancelled properly, the following Where K T/q=mv. at room temperature The condition to cancel the delta noise is l,'=Iwhich 0 gives the following equation:

so? v V, w I

comprising an nput signal including a delta noise s gnal.

5% anRC q Differentiation-Add FIG. 3 shows a block diagram for thisembodiment. Again, the delta noise decays exponentially. This circuitwill implement the following equation:

The noiseis represented by exp (t) and Vin(t) exp In FIG. 3, thedifferentiator 5 provides the differential and the summing circuit 6combines the output with the original signal from the gain circuit 7.

FIG. 4 is a typical schematic for implementing the block diagram of FIG.3.

The input signal is differentiated by the RC network. The differentiatedoutput is applied to the bases Q, and Q The emitter degenerationresistors RE determine the gain of the differentiator circuit. The inputsignal is simultaneously applied to Q and Q with their emitterdegeneration resistors RE determining the gain of the circuit. Theoverall circuit is similar to FIG. 2 with the multipliers ramp inputcurrent source replaced (Q of FIG. 2) by a constant current source 8.

For the circuit to function properly, the following equation should besatisfied:

RC=REIIRE2 What is claimed is: 1. Means for delta noise cancellation formemory systems means for differentiating said input signal, multipliermeans for multiplying the differentiated signal and a ramp function, asumming amplifier, means for applying the output of said mul tipliermeans to said amplifier and means for applying the input signal to saidamplifier.

i IR

1. Means for delta noise cancellation for memory systems comprising aninput signal including a delta noise signal, means for differentiatingsaid input signal, multiplier means for multiplying the differentiatedsignal and a ramp function, a summing amplifier, means for applying theoutput of said multiplier means to said amplifier and means for applyingthe input signal to said amplifier.